1. Technical Field
The present invention pertains to thermal treatment systems. In particular, the present invention pertains to detection of the presence of solution and/or leaks within a drape container of a thermal treatment system basin. The thermal treatment system thermally treats a sterile surgical liquid placed within the drape container and may be of the types disclosed in U.S. Pat. No. 4,393,659 (Keyes et al.), U.S. Pat. No. 4,934,152 (Templeton), U.S. Pat. No. 5,163,299 (Faries, Jr. et al.), U.S. Pat. No. 5,331,820 (Faries, Jr. et al.), U.S. Pat. No. 5,333,326 (Faries, Jr. et al.), U.S. Pat. No. 5,400,616 (Faries, Jr. et al.), U.S. Pat. No. 5,402,644 (Faries, Jr. et al.), U.S. Pat. No. 5,429,801 (Faries Jr. et al.), U.S. Pat. No. 5,457,962 (Faries, Jr. et al.), U.S. Pat. No. 5,502,980 (Faries, Jr. et al.), U.S. Pat. No. 5,522,095 (Faries, Jr. et al.), U.S. Pat. No. 5,524,643 (Faries, Jr. et al.), U.S. Pat. No. 5,551,240 (Faries, Jr. et al.), U.S. Pat. No. 5,615,423 (Faries, Jr. et al.), U.S. Pat. No. 5,653,938 (Faries, Jr. et al.), U.S. Pat. No. 5,809,788 (Faries, Jr. et al.), U.S. Pat. No. 5,816,252 (Faries, Jr. et al.), U.S. Pat. No. 5,857,467 (Faries, Jr. et al.), U.S. Pat. No. 5,862,672 (Faries, Jr. et al.), U.S. Pat. No. 5,879,621 (Faries, Jr. et al.), U.S. Pat. No. 5,950,438 (Faries, Jr. et al.), U.S. Pat. No. 6,003,328 (Faries, Jr. et al.), U.S. Pat. No. 6,035,855 (Faries, Jr. et al.), U.S. Pat. No. 6,087,636 (Faries, Jr. et al.), U.S. Pat. No. 6,091,058 (Faries, Jr. et al.), U.S. Pat. No. 6,255,627 (Faries, Jr. et al.), U.S. Pat. No. 6,371,121 (Faries, Jr. et al.), U.S. Pat. No. 6,860,271 (Faries, Jr. et al.), U.S. Pat. No. 6,918,395 (Faries, Jr. et al.) and U.S. Patent Application Publication Nos. 2004/0200483 (Faries, Jr. et al.) and 2004/0208780 (Faries, Jr. et al.). The disclosures in the above-mentioned patents and patent application publications are incorporated herein by reference in their entireties.
2. Discussion of the Related Art
The above-referenced Keyes et al. patent (U.S. Pat. No. 4,393,659) discloses a surgical slush producing system having a cabinet with a heat transfer basin at its top surface. A refrigeration mechanism in the cabinet takes the form of a closed refrigeration loop including: an evaporator in heat exchange relation to the outside surface of the heat transfer basin; a compressor; a condenser; and a refrigeration expansion control, all located within the cabinet. A separate product basin is configured to be removably received in the heat transfer basin. Spacers, in the form of short cylindrical stubs or buttons, are arranged in three groups spaced about the heat transfer basin and projecting into the heat transfer basin interior to maintain a prescribed space between the two basins. During use, that space contains a thermal transfer liquid, such as alcohol or glycol, serving as a thermal transfer medium between the two basins. A sterile drape, impervious to the thermal transfer medium, is disposed between the product basin exterior and the liquid thermal transfer medium to preserve the sterile nature of the product basin. Surgically sterile liquid, such as sodium chloride solution, is placed in the product basin and congeals on the side of that basin when the refrigeration unit is activated. A scraping tool is utilized to remove congealed sterile material from the product basin side to thereby form a slush of desired consistency within the product basin. Some users of the system employ the scraping tool to chip the solid pieces from the basin side.
As noted in the above-referenced Templeton patent (U.S. Pat. No. 4,934,152), the Keyes et al. system has a number of disadvantages. In particular, the separate product basin must be removed and re-sterilized after each use. Additionally, the glycol or other thermal transfer medium is highly flammable or toxic and, in any event, complicates the procedure. The Templeton patent (U.S. Pat. No. 4,934,152) discloses a solution to these problems by constructing an entirely new apparatus whereby the product basin is eliminated in favor of a sterile drape impervious to the sterile surgical liquid, the drape being made to conform to the basin and directly receive the sterile liquid. Congealed liquid is scraped or chipped from the sides of the conformed drape receptacle to form the desired surgical slush.
The Faries, Jr. et al. patent (U.S. Pat. No. 5,163,299) notes that scraping congealed liquid from the drape is undesirable in view of the potential for damage to the drape, resulting in a compromise of sterile conditions. As a solution to the problem, the Faries, Jr. et al. patent (U.S. Pat. No. 5,163,299) proposes that the drape be lifted or otherwise manipulated by hand to break up the congealed liquid adhering to the drape. Although this hand manipulation is somewhat effective, it is not optimal, and often is inconvenient and constitutes an additional chore for operating room personnel. Accordingly, several of the Faries, Jr. et al. patents (e.g., U.S. Pat. Nos. 5,331,820; 5,400,616; 5,457,962; 5,502,980; 5,653,938; 5,809,788; 5,857,467; 5,950,438; 6,003,328; and 6,035,855) resolve the problem of manual drape manipulation by disclosing various techniques and/or dislodgment mechanisms to automatically remove the congealed liquid adhering to the drape without endangering the integrity of the drape.
The Templeton patent (U.S. Pat. No. 4,934,152) further discloses an electrical heater disposed at the bottom of the basin to convert the sterile slush to warmed liquid, or to heat additional sterile liquid added to the basin. Templeton describes the need for such warm sterile liquid as occurring after a surgical procedure is completed to facilitate raising the body cavity of the surgery patient back to its normal temperature by contact with the warmed liquid. However, there are a number of instances during a surgical procedure when it is desirable to have simultaneous access to both warmed sterile liquid and sterile surgical slush. Accordingly, several of the Faries, Jr. et al. patents (e.g., U.S. Pat. Nos. 5,333,326; 5,429,801; 5,522,095; 5,524,643; 5,615,423; 5,653,938; 5,816,252; 5,862,672; 5,857,467; 5,879,621; 6,091,058; and 6,255,627) disclose a manner in which to simultaneously provide both surgical slush and warmed surgical liquid during a surgical procedure by utilizing a machine having plural basins with each basin either producing surgical slush or heating a sterile liquid. This machine typically utilizes a single surgical drape that forms a drape receptacle within each basin to collect sterile slush and heated sterile liquid produced by the machine in the respective basins.
In addition, several of the drapes and thermal treatment systems disclosed in the above-mentioned patents include specialized features to enhance various aspects of thermal treatment system operation. For example, some of the specialized features may include: bladder drapes (e.g., as disclosed in U.S. Pat. Nos. 5,809,788; 5,950,438; and 6,003,328); drapes having plates or disks (e.g., as disclosed in U.S. Pat. Nos. 5,457,962 and 5,502,980); reinforced drapes (e.g., as disclosed in U.S. Pat. No. 5,857,467); drape indicators and corresponding thermal treatment system detection devices to ensure sterility by enabling system operation in response to detecting a sterile drape placed on the system (e.g., as disclosed in U.S. Pat. Nos. 5,653,938 and 5,879,621); drapes having indicia to direct placement of the drapes on thermal treatment systems (e.g., as disclosed in U.S. Pat. No. 5,615,423); surgical drapes constructed of materials having a coefficient of friction in a particular range and/or drapes including attachment mechanisms such that a drape may withstand being drawn under a dislodgment mechanism (e.g., as disclosed in U.S. Pat. No. 6,035,855); a stand to elevate objects within a heated basin above the basin floor (e.g., as disclosed in U.S. Pat. No. 6,087,636) and/or a heater configured to cover a portion of the basin (e.g., as disclosed in U.S. Pat. Nos. 6,091,058 and 6,255,627) to prevent the drape from overheating and puncturing when objects are placed within the basin; and remote control of a thermal treatment system (e.g., as disclosed in U.S. Pat. Nos. 6,371,121, 6,860,271 and 6,918,395).
However, when insignificant amounts of liquid are present within a thermal treatment system basin, the system heating and cooling mechanisms operate with minimal thermal resistance, thereby enabling the mechanisms to become damaged. Further, the drapes employed by the system may be damaged by being disposed proximate the heating or cooling mechanism without having the liquid to absorb the thermal energy. Since only sterile drapes are to be used during surgical procedures, a leak in a surgical drape compromises sterility and contaminates the entire surgical procedure, thereby increasing the risk of injury to a patient.
The related art has attempted to overcome this problem by employing sensing devices with surgical drapes. For example, U.S. Pat. No. 5,524,643 (Faries, Jr. et al.) discloses a surgical drape combined with a sensor, preferably attached to the drape, to detect the presence of liquid within a drape container conforming to a heating/cooling thermal treatment system basin. An alternative embodiment employs sensors at opposite surfaces of the drape to measure conductance and, thereby, leakage through the drape. A microprocessor of each embodiment receives a signal representing, for example, an electrical conductance measurement and determines the presence of liquid and/or a leak. If liquid is not present or a leak is determined to exist, the microprocessor disables a temperature controller for the basin to prevent damage to the drape and heating and cooling mechanisms.
U.S. Pat. No. 5,816,252 (Faries, Jr. et al.) discloses a drape for use with a system for thermally treating a sterile medium. The drape includes liquid sensitive material that changes color upon contact with liquid to indicate the presence of a leak. The liquid sensitive material may be placed between the drape and a receiving basin or affixed to the drape in the form of indicia symbolically directing placement of the drape over the system. The system may include a single basin and be of the type that either thermally cools or heats the sterile medium, or the system may include a plurality of basins with each basin either thermally cooling or heating the sterile medium. The liquid sensitive material detects leaks within the drape while assisting the operator in properly aligning and placing the drape over the system.
The above-described systems can stand some improvement. In particular, the Faries, Jr. et al. sensor drape (U.S. Pat. No. 5,524,643) employs a plug connector disposed through the drape to facilitate connections between the drape sensor and the thermal treatment system, thereby complicating the process of effectively sealing the drape to prevent contamination of the sterile field. Further, the drape is required to be placed on the system with the plug aligned with a corresponding plug receptacle for system operation, thereby restricting the manners in which the drape may be positioned on the system to form the drape container. The Faries, Jr. et al. system employing liquid sensitive material with a drape (U.S. Pat. No. 5,816,252) indicates the presence of a leak within the drape container. However, this system relies on operating room personnel to respond to the leak indication and perform appropriate actions with respect to system operation. Thus, the system may continually operate in the presence of a drape container leak until personnel notice and respond to the leak indication, thereby increasing the risk of contamination of a surgical procedure and damage to the system heating or cooling mechanism when a drape leak occurs.